Power Converter

ABSTRACT

The object is to provide a power converter which is capable of minimizing an extent to which the power converter components other than the semiconductor module are thermally affected by the heat originating from the semiconductor module. 
     A casing houses: semiconductor modules constituting a main circuit for power conversion; a capacitor electrically connected to the main circuit; drive circuits that provide the main circuit with a drive signal used in power conversion operation; a control circuit that provides the drive circuit with a control signal used to prompt the drive circuit to provide the drive signal. Within the casing, a cooling chamber including a coolant passage is formed, and a chamber wall of the cooling chamber is formed with a thermally conductive material. At least the semiconductor modules are housed inside the cooling chamber, and at least the capacitor and the control circuit are disposed outside the cooling chamber.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/837,423, filed Mar. 15, 2013, which is a continuation of U.S.application Ser. No. 13/112,138, filed May 20, 2011, now U.S. Pat. No.8,411,441, granted Apr. 2, 2013, which is a continuation of U.S.application Ser. No. 12/161,151, filed Mar. 30, 2010, now U.S. Pat. No.7,969,735, granted Jun. 28, 2011, which is a National Stage of PCTInternational Application No. PCT/JP2007/050563, filed Jan. 17, 2007,which claims priority under 35 U.S.C. §119 to Japanese PatentApplication No. JP 2006-009154, filed Jan. 17, 2006, the entiredisclosures of which are herein expressly incorporated by reference.

TECHNICAL FIELD

The present invention relates to a power converter that converts inputpower to a specific type of power and outputs the power resulting fromthe conversion.

BACKGROUND ART

The background technologies related to power converters include theinverter device disclosed in patent reference literature 1. Patentreference literature 1 discloses a technology for miniaturizing aninverter device by stacking a switching element power module, asmoothing condenser and a control unit in this order via bases inside acase.

More specifically, patent reference literature 1 discloses a technologyfor controlling the braking force.

Patent reference literature 1: Japanese Laid Open Patent Publication No.2003-199363

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

Today, more than ever, the power converter installed in an automobile tocontrol the drive of a vehicle drive motor needs to be provided at lowercost, since a cost reduction achieved with regard to the power converterwill allow a less expensive motor drive system to be installed in thevehicle, which, in turn, will make possible to further popularize theuse of electric motors in vehicle drive. Through further promotion ofelectric motors in vehicle drive, the carbon footprint we leave on theglobal environment will be reduced and better fuel efficiency will beachieved.

A power converter may be provided at lower cost by, for instance,installing the power converter near the motor, e.g., at the casing ofthe transmission at which the motor is mounted, so as to eliminate theneed to install wiring for electrically connecting the power converterand the motor. This structure may be achieved by, for instance,miniaturizing the power converter through miniaturization of thesemiconductor module semiconductor chip constituting the powerconversion main circuit so as to allow the power converter to beinstalled at the transmission casing within the limited installationspace in the vehicle.

However, such miniaturization of the semiconductor chip is bound toresult in an increase in the heat generated at the semiconductor chip.As a result, the internal temperature at the power converter will risedue to the increase in the quantity of heat released from asemiconductor module into the power converter. This gives rise to aconcern that power converter components other than the semiconductormodule in the power converter constituted with the power convertercomponents including the semiconductor module disposed inside a singlecase are bound to be thermally affected. This issue is not addressed inthe background art described earlier. Accordingly, when miniaturizingthe power converter through miniaturization of the semiconductor chip,the extent to which the power converter components other than thesemiconductor module are thermally affected by the heat from thesemiconductor module needs to be mitigated.

Heat may also be generated at the semiconductor chip due to a lossoccurring as the semiconductor is switched. This factor should also betaken into consideration and the heat generation at the semiconductorchip should be minimized by reducing the extent of loss occurring duringthe switching operation at the semiconductor, so as to achieve theminiaturization of the semiconductor chip in a comprehensive manner. Itis crucial that the inductance at the connection conductor presentbetween a capacitor electrically connected to the semiconductor modulein order to further reduce the extent of loss occurring during thesemiconductor switching operation. In short, in a power converterprovided as a compact unit through miniaturization of the semiconductorchip, the extent to which the power converter components other than thesemiconductor module are thermally affected by the heat originating fromthe semiconductor module must be minimized by reducing the lossoccurring at the time of semiconductor switching operations and thusminimizing the heat generated at the semiconductor chip.

Means for Solving the Problems

The present invention provides a power converter in which the extent towhich a component other than the semiconductor module is thermallyaffected by heat originating from the semiconductor module can bemitigated.

The power converter according to the present invention includes asemiconductor module constituting a power conversion main circuit, acapacitor electrically connected to the main circuit, a drive circuitthat provides the main circuit with a drive signal used in powerconversion operation and a control circuit that provides the drivecircuit with a control signal used to prompt the drive circuit toprovide the drive signal, all housed inside a casing. Inside the casing,a cooling chamber, having formed therein a coolant passage and aperipheral wall thereof defining the chamber and constituted of athermally conductive material is formed. At least the semiconductormodule is housed inside the cooling chamber, whereas at least thecapacitor and the control circuit are disposed outside the coolingchamber.

Advantageous Effect of the Invention

According to the present invention, the semiconductor module is housedinside the cooling chamber with the peripheral wall thereof constitutedof a thermally conductive material. Thus, even if the heat released fromthe semiconductor module increases, the heat is not readily released tothe outside of the cooling chamber, which reduces at least the extent towhich the capacitor and the control circuit are thermally affected bythe heat from the semiconductor module. Consequently, the extent towhich the heat from the semiconductor module thermally affectscomponents other than the semiconductor module can be reduced byadopting the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 A sectional view showing the structure adopted in the inverterdevice unit achieved in a first embodiment

FIG. 2 A top plan view of the inverter device unit achieved in the firstembodiment

FIG. 3 A side elevation showing the structure adopted in the inverterdevice unit achieved in the first embodiment

FIG. 4 A side elevation showing the structure adopted in the inverterdevice unit achieved in the first embodiment

FIG. 5 A side elevation showing the structure adopted in the inverterdevice unit achieved in the first embodiment

FIG. 6 An exploded perspective showing the structure adopted in theinverter device unit achieved in the first embodiment

FIG. 7 A circuit diagram showing the electrical circuit structureadopted in the inverter device unit achieved in the first embodiment

FIG. 8 A block diagram showing the drive system in a hybrid electricvehicle that may adopt the inverter device unit in the first embodiment

FIG. 9 A sectional view showing the structure adopted in the inverterdevice unit achieved in a second embodiment

FIG. 10 A sectional view showing the structure adopted in the inverterdevice unit achieved in a third embodiment

FIG. 11 A sectional view showing the structure adopted in the inverterdevice unit achieved in a fourth embodiment

FIG. 12 A block diagram showing the drive system in a hybrid electricvehicle that may adopt the inverter device unit in the fourth embodiment

EXPLANATION OF REFERENCE NUMERALS

-   20, 30 semiconductor module-   50 capacitor-   70, 71 drive circuit board-   74 control circuit board-   110, 120, 160 inverter device

BEST MODE FOR CARRYING OUT THE INVENTION

The following is an explanation of the embodiments of the presentinvention, given in reference to the drawings.

The explanation below is given in reference to the embodiments on anexample in which a power converter according to the present inventionconstitutes an on-vehicle inverter device to be engaged in operationunder extremely rigorous conditions with regard to, in particular, theheat cycle, the operating environment and the like. An on-vehicleinverter device to function as a control device that controls the driveof an on-vehicle motor is installed in an on-vehicle electric system. Itconverts DC power supplied from an on-vehicle battery constituting anon-vehicle power source to a predetermined AC power and controls thedrive of the on-vehicle motor by supplying the AC power thus obtained tothe on-vehicle motor.

It is to be noted that the structure described below may be adopted in aDC-DC power converter such as a DC chopper or an AC-DC power converter.Furthermore, the structure described below may be adopted in anindustrial power converter to function as a motor control device used tocontrol a motor that drives production equipment or a home powerconverter that may be used in a residential solar power system or amotor control device for driving home appliances. It is particularlydesirable to adopt the present invention in a power converter to beprovided as an inexpensive compact unit.

First Embodiment

The first embodiment of the present invention is now described inreference to FIGS. 1 through 8.

In reference to FIG. 8, a hybrid electric vehicle achieved in theembodiment is described.

The hybrid electric vehicle (hereinafter referred to as an “HEV”)achieved in the embodiment, which is a type of electric vehicle,includes two drive systems. One of its drive systems is an engine systemthat uses an engine 104, i.e., an internal combustion engine, as itsmotive power source. The engine system is primarily utilized as an HEVdrive source. The other drive system is an on-vehicle electric systemthat uses motor generators 130 and 140 as its motive power source. Theon-vehicle electric system is mainly utilized as an HEV drive source anda power source that generates power to be used by the HEV.

At a front area of the vehicle body (not shown), a front axle 102 isaxially supported so as to rotate freely. A pair of front wheels 101 aremounted at the two ends of the front axle 102. Although not shown, arear axle with a pair of rear wheels mounted at the two ends thereof isaxially supported so as to rotate freely at a rear area of the vehiclebody. While the HEV in the embodiment adopts the front-wheel-drivesystem with the front wheels 101 driven as main wheels with motive powerand the rear wheels (not shown) free-wheeling, it may instead adopt arear wheel drive system, in which the rear wheels are driven as mainwheels.

A front wheel-side differential gear (hereafter referred to as a “frontwheel-side DEF”) 103 is mounted at a central position of the front axle102. The front axle 102 is mechanically connected to the output side ofthe front wheel-side DEF 103. And output shaft of a transmission 105 ismechanically connected to the input side of the front wheel-side DEF103. The front wheel-side DEF 103 is a differential power transfermechanism that distributes the rotational drive force having undergonespeed change at the transmission 105 and transmitted from thetransmission 105 to the left and right ends of the front axle 102. Theoutput side of the motor generator 130 is mechanically connected to theinput side of the transmission 105. The output side of the engine 104and the output side of the motor generator 140 are mechanicallyconnected via a power transfer mechanism 150 to the input side of themotor generator 130.

It is to be noted that the motor generators 130 and 140 and the powertransfer mechanism 150 are all housed inside a casing of thetransmission 105.

The power transfer mechanism 150 is a differential mechanism constitutedwith gears 151 through 158. The gears 153 through 156 among these gearsare bevel gears. The gears 151, 152, 157 and 158 are spur gears. Thepower generated at the motor generator 130 is directly transmitted tothe transmission 150. The motor generator 130 is mounted coaxially withthe gear 157. Thus, if no drive power is supplied to the motor generator130, the power transmitted to the gear 157 is directly transmitted tothe input side of the transmission 105. As the engine 104 starts up andthe gear 151 is driven, the power from the engine 104 is transmittedfrom the gear 151 to the gear 152, then from the gear 152 to the gears154 and 156, from the gears 154 and 156 to the gear 158 and finally tothe gear 157. As the motor generator 140 is engaged in operation and thegear 153 is driven, the rotation of the motor generator 140 istransmitted from the gear 153 to the gears 154 and 156, then from thegears 154 and 156 to the gear 158 and finally to the gear 157.

It is to be noted that the power transfer mechanism 150 may be anothertype of mechanism such as a planetary gear mechanism.

The motor generator 130 is a synchronous machine that includes a rotorequipped with a permanent magnet for magnetic field generation. It isdriven as an inverter device 110 controls AC power supplied to anarmature coil at a stator. The motor generator 140 is also a synchronousmachine similar to the motor generator 130 and its drive is controlledby an inverter device 120. A battery 106 is electrically connected tothe inverter devices 110 and 120 and thus, electrical power can besupplied from the battery 106 to the inverter devices 110 and 120 andpower can also be supplied from the inverter devices 110 and 120 to thebattery 106.

The HEV in the embodiment includes two power generation units, i.e., afirst motor generator unit constituted with the motor generator 130 andthe inverter device 110 and a second motor generator unit constitutedwith the motor generator 140 and the inverter device 120, which areselectively engaged in operation in correspondence to the driving state.Namely, the drive torque of the vehicle being driven with the motivepower originating from the engine 104 can be assisted by starting up thesecond motor generator unit with the motive power from the engine 104 toengage it in operation as a power generation unit to generate electricpower and by engaging the first motor generator unit in operation as amotor unit with the electric power generated via the second motorgenerator unit. In addition, the vehicle speed of the vehicle beingdriven with power from the engine can be assisted by starting up thefirst motor generator unit as a generator unit to generate power withthe power from the engine 104 and by engaging the second motor generatorunit in operation as a motor unit with the electric power generated viathe first motor generator unit.

Furthermore, the first motor generator unit can be engaged in operationas a motor unit with electric power supplied from the battery 106 andthus, the vehicle can be driven with the motive power from the motorgenerator 130 alone in the embodiment.

Moreover, the battery 106 can be charged with electric power generatedby engaging the first motor generator unit or the second motor generatorunit in operation as a power generation unit with motive power from theengine 104 or power originating from the wheels in the embodiment.

Next, the electrical circuit structure adopted in conjunction with theinverter devices 110 and 120 in the embodiment is explained in referenceto FIG. 7.

The inverter devices 110 and 120 in the embodiment are provided as asingle integrated inverter device unit. The inverter device unitincludes a semiconductor module 20 of the inverter device 110, asemiconductor module 30 of the inverter device 120, a capacitor 50, adrive circuit 92 mounted at a drive circuit board 70 of the inverterdevice 110, a drive circuit 94 mounted at a drive circuit board 71 ofthe inverter device 120, a control circuit mounted at a control circuitboard 74, a connector 73 and a drive circuit 91 that drives a dischargecircuit (not shown) of the capacitor 50, both mounted at a connectorboard 72, and current sensors 95 and 96.

It is to be noted that in the illustration of the embodiment, the powersystem is indicated by solid lines and the signal system is indicated bydotted lines so as to indicate them as distinct from each other.

The semiconductor modules 20 and 30 respectively constitute powerconversion main circuits in the corresponding inverter devices 110 and120 and each includes a plurality of switching power semiconductorelements. The semiconductor modules 20 and 30 engage in operation inresponse to drive signals output from the corresponding drive circuits92 and 94, convert DC power supplied from a high-voltage battery HBA tothree-phase AC power and supply the power resulting from the conversionto armature coils of the corresponding motor generators 130 and 140. Themain circuits are each structured as a three-phase bridge circuit withserial circuits, each corresponding to one of the three phases,connected electrically parallel to one another between the positivepole-side and the negative pole-side of the battery 106.

The serial circuits, which are also referred to as arms, are each formedby electrically serially connecting an upper arm-side switching powersemiconductor element and a lower arm-side switching power semiconductorelement. The switching power semiconductor elements used in theembodiment are IGBTs (insulated gate-type bipolar transistors) 21. AnIGBT 21 includes three electrodes, i.e., a collector electrode, anemitter electrode and a gate electrode. Between the collector electrodeand the emitter electrode, a diode 38 is electrically connected at theIGBT 21. The diode 38 includes two electrodes, i.e., a cathode electrodeand an anode electrode and the cathode electrode is electricallyconnected to the collector electrode of the IGBT 21 and the anodeelectrode is electrically connected to the emitter electrode of the IGBT21 so as to set the direction running from the emitter electrode towardthe collector electrode at the IGBT 21 along the forward direction.

Alternatively, the switching power semiconductor elements may be MOSFETs(metal oxide semiconductor field effect transistors). A MOSFET includesthree electrodes, i.e., a drain electrode, a source electrode and a gateelectrode. It is to be noted that since a MOSFET includes an incidentaldiode present between the source electrode and the drain electrode andassuming a forward direction running from the drain electrode toward thesource electrode, there is no need to install a special diode and inthis sense, it is different from an IGBT.

The arms corresponding to the individual phases are each formed byelectrically serially connecting the source electrode of an IGBT 21 withthe drain electrode of another IGBT 21. It is to be noted that while theillustration of the embodiment shows a single IGBT constituting an upperor lower arm in correspondence to each phase, a plurality of IGBTsconnected electrically in parallel to one another may constitute anupper or lower arm. As detailed later, an upper or lower armcorresponding to each phase is constituted with three IGBTs in theembodiment.

The drain electrode of the IGBT 21 constituting the upper arm in eachphase is electrically connected to the battery 106 on the positivepole-side, whereas the source electrode of the IGBT 21 constituting thelower arm in correspondence to each phase is electrically connected tothe battery 106 on the negative pole-side. The neutral point between thetwo arms in each phase (the connection area where the source electrodeat the upper arm IGBT and the drain electrode at the lower arm IGBT areconnected with each other) is electrically connected to the armaturecoil in the corresponding phase at the corresponding motor generator 130or 140.

The drive circuits 92 and 94 respectively constitute the drive units forthe corresponding inverter devices 110 and 120 and generate drivesignals to be used to drive the IGBTs 21 based upon a control signal(control value) output from the control circuit 93. The drive signalsgenerated in the respective circuits are output to the correspondingsemiconductor modules 20 and 30. The drive circuits 92 and 94 are eachconstituted with a 6-in-1 type integrated circuit formed by integratinga plurality of circuits corresponding to the upper and lower arms in theindividual phases into a single circuit. The circuits corresponding tothe upper and lower arms in each phase include, for instance, aninterface circuit, a gate circuit and an error detection circuit.

The control circuit 93, which functions as a control unit for theinverter devices 110 and 120, is constituted with a microcomputer thatgenerates through arithmetic operation a control signal (control value)based upon which the plurality of switching power semiconductor elementsare engaged in operation (turned on/off). Sensor signals (sensor values)provided from the current sensors 95 and 96 and rotation sensors mountedat the motor generators 130 and 140, as well as a torque command signal(a torque command value) provided from a higher-order control device,are input to the control circuit 93. Based upon the signals inputthereto as described above, the control circuit 93 generates a controlsignal (control value) through arithmetic operation and outputs thecontrol signal thus generated to the drive circuits 92 and 94.

The connector 73 electrically connects the internal components in theinverter devices 110 and 120 with an external control device.

The capacitor 50, which functions as a smoothing circuit for minimizingthe extent of DC voltage fluctuation bound to occur as the IGBTs 21 areengaged in operation, is connected electrically parallel to the DC-sideof the semiconductor modules 20 and 30.

The drive circuit 91 drives a discharge circuit (not shown) via whichthe electrical charge collected at the capacitor 50 is discharged.

Next, the actual structure adopted in the inverter devices 110 and 120is described in reference to FIGS. 1 through 6.

The inverter device unit in the embodiment includes a casing (invertercase) formed by stacking a second base 12 atop a lower case 13, a firstbase 11 atop the second base and an upper case 10 atop the first base11. The casing is a rectangular parallelepiped container taking onrounded contours as a whole. The components constituting the casing areall constituted with a thermally conductive aluminum material.

The internal space inside the casing is separated into two spaces alongthe vertical direction via the plate-like first base 11 and the pi(π)-shaped second base 12 and two cooling chambers with all theirperipheral boundaries (peripheral walls, ceilings and floors) defined bythermally conductive members are formed in the casing. Two coolantpassages 28, through which coolant (cooling water) is to flow, areformed at the first base 11 and the second base 12 forming a partitionwall separating the two cooling chambers. The two cooling chambers inthe casing structured as described above are thermally isolated fromeach other. Namely, the extent to which one coolant is thermallyaffected by the other cooling chamber is minimized.

In the upper cooling chamber within the casing, the semiconductormodules 20 and 30 assuming a shape and size with a significantmeasurement taken along the longer side of the casing and a lesssignificant measurement taken along the shorter side of the casing, arehoused side-by-side along the direction in which the shorter side of thecasing extends, above the coolant passages 28. This thermally connectsthe semiconductor modules 20 and 30 with the coolant passages 28,allowing the heat generated as the IGBTs 21 are engaged in operation tobe absorbed via the coolant. As a result, the extent to which the heatreleased from the semiconductor modules 20 and 30 affects the coolingchamber present below can be reduced.

At a side end surface of the casing on one side along the longer sidethereof, an intake piping 15 communicating with one of the coolantpassages 28 and an outlet piping 16 communicating with the other coolantpassage 28 are disposed. The coolant passages 28 extend parallel to oneanother from one side of the casing toward the other side along thelonger side thereof and are in communication with each other at the endof the casing on the other side along the longer side of the casing.Namely, the coolant passages 28 together form a U-shape.

Heat transfer plates 23 are each disposed over the area where a coolantpassage 28 is formed at the first base 11. The heat transfer plate 23 isa rectangular plate ranging from one side of the casing along the longerside thereof toward the other side along the coolant passage 28 andconstitutes a surface of the coolant passage 28. The heat transfer plate23 is thus directly cooled by the coolant flowing through the coolantpassage 28. The heat transfer plate 23 is constituted of a thermallyconductive material such as aluminum or copper, with cooling fins (notshown) projecting out into the coolant passage 28 formed at its surfacetoward the coolant passage 28. As a result, it is cooled by the coolantover a large cooling area so as to improve the cooling effect of thecoolant.

Module cases 24 are disposed so as to range upright along the outeredges of the heat transfer plates 23 at the upper surfaces of theindividual heat transfer plates 23. The module cases 24 each form threehousing chambers in the space above the upper surface of thecorresponding heat transfer plate 23 split via the module case intothree areas along the longer side of the casing so as to house the IGBTs21 and the diodes 38 in correspondence to the individual phases.

At the sidewall ranging along the longer side of each module case 24,facing opposite the semiconductor module 20 or 30, a DC positivepole-side module terminals 33 and a DC negative pole-side moduleterminals 26 are disposed in correspondence to each housing chamber. TheDC positive pole-side module terminals 33 and the DC negative pole-sidemodule terminals 26 project out upward beyond the side wall of eachmodule case 24. The sides of the DC positive pole-side module terminals33 and the DC negative pole-side module terminals 26 opposite from theprojecting sides extend to the inner space in the housing chamber withtheir surfaces exposed at the surface of the module case 24. As aresult, a DC positive pole-side module electrode 36 and a DC negativepole-side module electrode 37 are formed within each housing chamber.

At the side wall ranging along the longer side of each module case 24,located on the side opposite from the side facing the semiconductormodule 20 or 30, an AC module terminals 27 is disposed in correspondenceto each housing chamber. The AC module terminals 27 projects out upwardbeyond the side wall of the module case 24. The side of the AC moduleterminals 27 opposite from the projected side extends to the inner spaceof the housing chamber and its surface is exposed over the surface ofthe module case 24. As a result, an AC module electrode 35 is formedinside each housing chamber.

Two insulating substrates 22 are disposed side-by-side in correspondenceto each housing chamber along the longer side of the casing at the uppersurface of the heat transfer plate 23. Two plate-like wiring members 39are disposed side-by-side along the longer side of the casing at theupper surface of each insulating substrate 22. One of the wiring members39 disposed at one of the two insulating substrates 22 in each housingchamber is electrically connected with the DC positive pole-side moduleelectrode 36. One of the wiring members 39 disposed at the otherinsulating substrate 22 in each housing chamber is electricallyconnected with the DC negative pole-side module electrode 37. The otherwiring members 39 at the two insulating substrates 22 in each housingchamber are electrically connected with the AC module electrode 35. Theyare electrically connected with the respective electrodes viaelectrically conductive wire 29.

At the upper surface of one of the wiring members 39 at each of the twoinsulating substrates 22 in each housing chamber, three IGBT/diode seteach constituted with an IGBT 21 and a diode 38 disposed side-by-sidealong the longer side of the casing, are set side-by-side along theshorter side of casing. The upper and lower arms are thus formed incorrespondence to the individual phases. The IGBTs 21 and the diodes 38are electrically connected with the wiring members 39 which iselectrically connected with the AC module electrode 35. The gateelectrodes of the IGBTs 21 are electrically connected to connectors 25.These electrical connections are achieved via electrically conductivewire 29. The connectors 25 are each disposed at one of the foursidewalls defining three separate areas above the upper surface of eachheat transfer plate 23 at the module case 24.

A plate-like module case lid 34 is disposed at the top of each modulecase 24. The module case lid 34 forms a ceiling that covers the open topof the module case 24 so as to seal off the housing chambers and isconstituted of the same material as that constituting the module case24, i.e., an insulating resin. At the upper surface of the module caselid 34, a wiring sheet 31 and a wiring connector 32 electricallyconnected to the wiring sheet 31 are disposed. The wiring sheet 31 iselectrically connected with the connectors 25 projecting upward viathrough holes formed at the module case lid 34. The wiring connector 32is electrically connected with the drive circuits 92 and 94 at the drivecircuit boards 70 and 71 via wirings (not shown).

The capacitor 50, the drive circuit board 70 and 71, the control board74 and the connector board 72 are housed inside the cooling chamberlocated toward the bottom of the casing.

The capacitor 50 is disposed toward the bottom side at the center (thearea enclosed by the two legs of the n) of the second base 12, at aposition in close proximity to the DC-side of the semiconductor modules20 and 30. The capacitor 50 is constituted with four electrolyticcapacitors with their sections taken along the height of the casingassuming an elliptical shape. The four electrolytic capacitors aredisposed so that their longer sides are aligned with the longer side ofthe casing with two electrolytic capacitors set side-by-side both alongthe longer side and along the shorter side of the casing. They arehoused inside a capacitor case 51 via a holding band 52. The capacitorcase 51 is a thermally conductive container with an open top, with aflange portion at the top of the case set in contact with the lower endsof the two legs of the π shape assumed at the second base 12. Thus, thecapacitor 50 is thermally connected with the coolant passages and thecapacitor 50 can be cooled with the coolant.

The electrolytic capacitors each include a positive pole-side capacitorterminal 57 and a negative pole-side capacitor terminal 56 passingthrough a capacitor lid 54 closing off the open top of a capacitor case53. The positive pole-side capacitor terminal 57 and the negativepole-side capacitor terminal 56, both assuming the shape of a plate,face opposite each other along the shorter side and a plate-likeinsulating member 55 formed as an integrated part of the capacitor lid54 is held between the capacitor terminals 57 and 56 from the shorterside. The capacitor terminals are set so that capacitor terminalsadjacent to each other along the shorter side will assume positions notin line with each other along the longer side when the four electrolyticcapacitors are housed inside the capacitor case 53.

The drive circuit board 70 is disposed toward the bottom of the secondbase 12 on the side where the semiconductor module 20 is present, overan area enclosed by one of the two legs of the π shape and the flangeportion of the second base 12. The drive circuit board 71 is disposedtoward the bottom of the second base 12 on the side where thesemiconductor module 30 is present, over an area enclosed by the otherleg of the π shape and flange portion of the second base 12. The drivecircuit boards 70 and 71 are thermally connected with the second base12. Thus, the drive circuit boards 70 and 71 are thermally connectedwith the coolant passages 28 and the drive circuit boards 70 and 71 canbe cooled with the coolant in the coolant passages.

The control circuit board 74 is disposed so as to face opposite the sidesurface of the capacitor case 53 on one side (toward the semiconductormodule 30) along the shorter side of the capacitor case. The controlcircuit board 74 is thermally connected with the second base 12. Sincethis allows the control circuit board 74 to be thermally connected witha coolant passage 28, the control circuit board 74 can be cooled withthe coolant.

The connector board 72 is disposed so as to face opposite the sidesurface of the capacitor case 53 on the other side (toward thesemiconductor module 20) along the shorter side of the capacitor case.The connector board 72 is thermally connected with the second base 12.Since this allows the connector board 72 to be thermally connected witha coolant passage 28, the connector board 72 can be cooled with thecoolant. A connector 73 on the other side projects to the outsidethrough a side end surface of the casing along the lengthwise direction.

The capacitor 50 is electrically connected with the semiconductormodules 20 and 30 via a DC-side connecting conductor 40. The DC-sideconnecting conductor 40 extends to the upper cooling chamber and thelower cooling chamber via a through hole passing through the first base11 and the second base along the height of the casing, which is formedas an elongated hole (elongated along the longer side of the casing) topass through the central areas of the first base and the second base.

The DC-side connecting conductor 40 is a wiring member adopting alaminated structure that includes a plate-like DC positive pole-side busbar 45 extending along the longer side of the casing and a plate-like DCnegative pole-side bus bar 44 ranging along the longer side of thecasing, laminated one on top of the other via an insulating sheet 43along the shorter side of the casing, with DC positive pole-side moduleterminals 42 and a positive pole-side capacitor terminal 46 formed asintegrated part of the DC positive pole-side bus bar 45 and DC negativepole-side module terminals 41 and negative pole-side capacitor terminals47 formed as integrated part of the DC negative pole-side bus bar 44. Byadopting this structure, the inductance between the capacitor 50 and thesemiconductor modules 20 and 30 can be lowered, which, in turn, inhibitsheat generation due to the loss occurring as the IGBTs 21 are switched.

The DC positive pole-side module terminals 42 are electrically connectedwith the DC positive pole-side module terminals 33, as the DC positivepole-side module terminals 42 extends upward from the top of the DCpositive pole-side bus bar 45 at the position at which the DC positivepole-side module terminals 33 project upward from the module case 24 andthe DC positive pole-side module terminals 42 facing opposite the DCpositive pole-side module terminals 33 along the shorter side of thecasing are fixed onto the DC positive pole-side module terminals 33 viafixing means such as screws. The DC negative pole-side module terminals41 are electrically connected with the DC negative pole-side moduleterminals 26, as the DC negative pole-side module terminals 41 extendupward from the top of the DC negative pole-side bus bar 44 at thepositions at which the DC negative pole-side module terminals 26 projectupward from the module case 24 and the DC negative pole-side moduleterminals 41 facing opposite the DC negative pole-side module terminals26 along the shorter side of the casing are fixed onto the DC negativepole-side module terminals 26 via fixing means such as screws.

The positive pole-side capacitor terminals 46 and the negative pole-sidecapacitor terminals 47 extend downward through the bottoms of the DCpositive pole-side bus bar 45 and the DC negative pole-side bus bar 44at the positions at which the capacitor terminals project out so as toclamp the capacitor terminals from the shorter side of the casing alongthe shorter side of the casing and are fixed to the capacitor terminalswith the matching polarities facing opposite them via fixing means suchas screws, thereby becoming electrically connected to the capacitorterminals with the matching polarities. By adopting this wiringstructure, the positive pole side and the negative pole side can be setfacing opposite each other over the wiring area extending from the DCpositive pole-side bus bar 45 and the DC negative pole-side bus bar 44to the individual capacitor terminals. With such a wiring member, theinductance is further reduced so as to further inhibit heat generationdue to the loss occurring as the IGBTs 21 are switched.

A DC terminal 80 is disposed at an end of the casing on the other sidealong the longer side of the casing. The DC terminal 80 includes a DCpositive pole-side external terminal 82, a DC negative pole-sideexternal terminal 81, a DC positive pole-side connector terminal 86, aDC negative pole-side connector terminal 85, a DC positive pole-side busbar 84 which connects the DC positive pole-side external terminal 82 andthe DC positive pole-side connector terminal 86 and a DC negativepole-side bus bar 83 which connects the DC negative pole-side externalterminal 81 with the DC negative pole-side connector terminal 85.

The DC positive pole-side external terminal 82 and the DC negativepole-side external terminal 81 are electrically connected with anexternal cable extending via a connector mounted at a through hole 17formed at a side end surface of the casing on the other side along thelengthwise direction. The DC positive pole-side bus bar 84 and the DCnegative pole-side bus bar 83 extend toward the semiconductor modules 20and 30 so as to face opposite each other along the shorter side of thecasing. The DC positive pole-side connector terminal 86 is electricallyconnected to the DC positive pole-side module terminals 33 and 42,whereas the DC negative pole-side connector terminal 85 is electricallyconnected to the DC negative pole-side module terminals 26 and 41.

A hole 18 formed at the upper surface of the upper case 10 is used whenconnecting the DC positive pole-side external terminal 82 and the DCnegative pole-side external terminal 81 to an external cable and isblocked off with a lid at all times except while connecting theterminals to the external cable.

Inside the casing, an AC bus bar 60 for the three phases is disposed ateach of the two ends along the shorter side of the casing. The AC busbar 60 extends from the lower cooling chamber to the upper coolingchamber via a vertical (along the height of the casing) through holeformed through the first base 11 and the second base 12 at an end of thecasing along the shorter side thereof. AC-side module terminals 61 areformed at one end of the AC bus bar 60 at the upper cooling chamber. TheAC-side module terminals 61 face opposite the AC-side module terminals27 along the shorter side of the casing and are electrically connectedto the AC-side module terminals 27 via fixing means such as screwsfixing the AC-side module terminals 61 to the AC-side module terminals27. External connector terminals 62 via which connection with theexternal cables extending to the motor generators 130 and 140 isachieved are formed at the other end of the AC bus bar 60 in the lowercooling chamber and the external connector terminals 62 are held byterminal holders 63.

It is to be noted that reference numeral 14 indicates a mounting leg viawhich the inverter device unit casing is fixed onto the casing of thetransmission 105 or to the casing of the engine 104 and the transmission105. The mounting legs are formed by using a rigid material such as SUSto assure sufficient strength. In addition, they assume a bent shape soas to achieve elasticity in order to damp vibration from thetransmission 15 and the engine 104.

In the embodiment described above, a cooling chamber, the entireperiphery of which is defined by a thermally conductive member, isformed inside the inverter device unit casing and the semiconductormodules 20 and 30 are housed inside this chamber. Thus, even if agreater quantity of heat is generated at the compact IGBTs 21 and moreheat is released from the semiconductor modules 20 and 30, the heat isnot let out of the cooling chamber. As a result, the extent to which theother components of the inverter device, such as the capacitor 50, arethermally affected can be minimized.

Second Embodiment

The second embodiment of the present invention is now described inreference to FIG. 9.

Since the second embodiment is achieved by modifying the firstembodiment, the same reference numerals are assigned to identicalcomponents and their explanation is omitted.

This embodiment differs from the first embodiment in that a thirdcooling chamber, enclosed in its entirety by the upper case 10 and asecond upper case 19, is formed above the cooling chamber in which thesemiconductor modules 20 and 30 are housed and that aboard 97 formed byintegrating the drive circuit board, the control circuit board and theconnector board into a single board is housed inside the third coolingchamber.

The wiring sheets at the semiconductor modules 20 and 30 areelectrically connected to the board 97 via wiring members 98.

The structure achieved in the second embodiment does not include acapacitor case for the capacitor 50 and the legs of the π-shaped secondbase 12 are used in place of the capacitor case. For this reason, thelegs of the π-shaped second base 12 extend to the bottom of the lowercase 13.

In addition, the mounting legs 14 assume a hollow structure and powercables 64 electrically connected to the AC external terminals 62 arethreaded through the hollow mounting legs to be led into the casing ofthe transmission 105. By adopting this structure, the power cables 64led into the casing of the transmission 105 with ease can then beconnected to the motor generators 130 and 140.

The embodiment achieves an advantage similar to that of the precedingembodiment in that even when a greater quantity of heat is generated atthe compact IGBTs 21 and more heat is released from the semiconductormodules 20 and 30, the heat is not readily let out of the coolingchamber, so as to minimize the extent to which other components of theinverter device, such as the capacitor 50, are thermally affected.

Third Embodiment

The third embodiment of the present invention is now described inreference to FIG. 10.

Since the third embodiment is achieved by modifying the firstembodiment, the same reference numerals are assigned to identicalcomponents and their explanation is omitted.

The third embodiment differs from the first embodiment in that the drivecircuit boards 70 and 71, the AC bus bar 60 and the terminal holders 63are housed together with the semiconductor modules 20 and 30 in thecooling chamber.

In addition, a second cooling chamber, defined by the second base 12, isformed under the cooling chamber housing the semiconductor modules 20and 30 and two third cooling chambers, defined by the second base 12,are formed under the second cooling chamber. The capacitor 50 is housedin the second cooling chamber, the control circuit board 74 is housed inone of the third cooling chambers and the connector board 72 is housedinside the other third cooling chamber. The capacitor 50 is installedwith a lateral orientation in two split parts separated from each otheralong the shorter side of the casing. Accordingly, the DC-sideconnecting conductor 40, too, is divided into a part located on the sidetoward the semiconductor module 20 and a part located on the side towardthe semiconductor module 30. It is to be noted that while the DC-sideconnecting conductor 40 assumes a structure similar to that in the firstembodiment, the bends at the individual terminals are partiallymodified. In addition, DC positive pole-side external terminals 82 andDC negative pole-side external terminals 81 are formed at the DC-sideconnecting conductor 40 as integrated parts thereof.

It is to be noted that reference numeral 99 indicates connector wiringthat electrically connects the drive circuit board 70 or 71 with awiring sheet 31.

The embodiment achieves an advantage similar to that of the precedingembodiments in that even when a greater quantity of heat is generated atthe compact IGBTs 21 and more heat is released from the semiconductormodules 20 and 30, the heat is not readily let out of the coolingchamber, so as to minimize the extent to which other components of theinverter device, such as the capacitor 50, are thermally affected.

Fourth Embodiment

The fourth embodiment of the present invention is now described inreference to FIGS. 11 and 12.

Since the fourth embodiment is achieved by modifying the firstembodiment, the same reference numerals are assigned to identicalcomponents and their explanation is omitted.

The fourth embodiment differs from the third embodiment in that a motorgenerator 160 is utilized to drive the rear wheels 201. Accordingly, thestructure achieved in the embodiment includes a single inverter deviceunit 150. The speed of the motive power originating from the motorgenerator 160 is reduced at a speed-reducer 204, is transmitted to arear-side differential gear 203 and is then transmitted from therear-side differential gear 203 to the rear axle 202. Namely, the fourthembodiment provides a four-wheel-drive hybrid vehicle. The inverterdevice 150 is connected to the battery 106. When the motor generator 160is utilized as an electric motor, electric power is supplied from thebattery 106 to the inverter device 150, whereas when it is utilized as agenerator, electric power is supplied from the inverter device 150 tothe battery 106.

The inverter device 150 adopts a structure equivalent to the left halfof the inverter device unit in the third embodiment ranging to the leftbeyond the center of the casing along the shorter side thereof, with athird cooling chamber formed above the cooling chamber housing thesemiconductor module 30, as in the inverter device unit achieved in thesecond embodiment. A board 97, achieved by integrating the drive circuitboards, the control circuit board and the connector board into a singleboard, is housed inside the third cooling chamber.

In addition, the power cables 64 are led into the casing of thetransmission 105 through the hollow mounting legs 14 as in the inverterdevice unit in the second embodiment.

The inverter device 150 may adopt a structure that is an exactequivalent to the left half or the right half of the inverter deviceunit achieved in any of the first through third embodiments ranging tothe left or the right from the center of the casing along the shorterside thereof.

The embodiment achieves an advantage similar to that of the precedingembodiments in that even when a greater quantity of heat is generated atthe compact IGBTs 21 and more heat is released from the semiconductormodules 20 and 30, the heat is not readily let out of the coolingchamber, so as to minimize the extent to which other components of theinverter device, such as the capacitor 50, are thermally affected.

1. A power converter, comprising: a semiconductor module that comprisesa power semiconductor element to convert DC power to AC power; anAC-side connecting conductor that transmits the AC power; and a passageforming body that is constructed of a thermally conductive member andforms a coolant passage through which coolant flows, wherein the passageforming body is provided with a through hole for communicating theAC-side connecting conductor therein.
 2. The power converter accordingto claim 1, further comprising: a case that defines a housing space forhousing the semiconductor module and is provided with an openingportion, wherein the opening portion of the case is closed by thepassage forming body in a state in which the semiconductor module ishoused in the housing space of the case.
 3. The power converteraccording to claim 2, wherein the AC-side connecting conductor comprisesa U-phase connecting conductor, a V-phase connecting conductor and aW-phase connecting conductor, and the passage forming body is providedwith a first through hole for communicating the U-phase connectingconductor, a second through hole for communicating the V-phaseconnecting conductor and a third through hole for communicating theW-phase connecting conductor.
 4. The power converter according to claim3, wherein the first through hole, the second through hole and the thirdthrough hole are arranged along a direction in which the coolant flows.5. The power converter according to claim 2, further comprising: an ACterminal holder that holds the AC-side connecting conductor, wherein thesemiconductor module is disposed at one side of the passage forming bodyand the AC terminal holder is disposed at another side of the passageforming body, opposite to the semiconductor module via the passageforming body.
 6. The power converter according to claim 2, wherein thesemiconductor module is disposed at one side of the passage formingbody, the passage forming body is provided with an opening thatcommunicates with the passage at the side of the passage forming bodywhere the semiconductor module is disposed, the semiconductor module isprovided with a heat transfer plate on which the power semiconductorelement is mounted via an insulating substrate, and the heat transferplate closes the opening so as to directly contact with the coolant.